Method and device for heating preform

ABSTRACT

While blowing out cooling air to a preform which is biaxially stretched and blow molded into a bottle shape, heat sources are made operative by a high power and the first heating process as quick heating is performed to the preform. Subsequently, the heated preform is left as it is and a temperature adjusting process to reduce a temperature difference between an outer surface temperature and an inner surface temperature of the preform to a predetermined value or less is executed. The second heating process to heat the preform until the outer surface temperature is equal to a temperature which is slightly lower than a crystallization temperature of the PET is executed to the preform obtained after completion of the temperature adjusting process while blowing out the cooling air to the preform. Thus, the quick heating of the preform is safely accomplished without causing an overheating state.

TECHNICAL FIELD

The invention relates to method and device for heating a preform whichis biaxially stretched and blow molded into a bottle shape, in which thepreform is injection molded into a cylindrical shape with a bottom by apolyethylene terephthalate resin (hereinafter, simply abbreviated toPET) and is biaxially stretched and blow molded into the bottle shape.

BACKGROUND ART

For biaxial stretching blow molding of a preform as an injection moldedproduct made of the PET into a bottle shape, it is necessary to heat thepreform to a temperature at which it can be stretched. As a method ofheating the preform, there are a method of heating it by a heat transferfrom a temperature of an atmosphere and a method of heating it byabsorption of light.

According to the method of heating the preform by the heat transfer fromthe atmosphere temperature, since a coefficient of thermal conductivityof the PET material is slightly lower, it takes a long time to heat thewhole preform including an inner surface to a desired temperature. Onthe other hand, according to the method of heating the preform by thelight absorption, since the preform is heated by the light of awavelength which penetrates into the inner surface of the preform, atime which is necessary for heating the whole preform including theinner surface to the desired temperature or higher is shorter than thatof the heating means by the heat transfer mentioned above.

As mentioned above, upon heating of the preform at the time of thebiaxial stretching blow molding of the bottle, as disclosed inJP-A-11-42702, an infrared lamp (near infrared heater) for generatingnear infrared rays is generally used as a heat source. A plurality ofnear infrared heaters are arranged in parallel along the axial centerdirection of the conveyed preform and a power of each near infraredheater is adjusted, thereby heating the preform in accordance with adesired temperature distribution along the axial center.

However, even if the near infrared heaters are used as heating sourcesof the preform or another proper heat source (for example, a sheathheater or the like) is used, since the preform is heated from itsoutside, the following problem exists. That is, a temperature risingspeed on the outer surface side of the preform is certainly higher thanthat on the inner surface side, a temperature difference occurs betweenthe outside and the inside of the preform which is heated, if thetemperature difference is large, the proper biaxial stretching blowmolding operation cannot be performed, so that it is necessary to limitthe power of the heat sources in order to suppress the heatingtemperature difference between the inner surface side and the outersurface side of the preform to a predetermined value or less. Thus,heating time of the preform cannot be sufficiently shortened.

A technique using both of near infrared heating means and dielectricheating means in order to shorten the heating time of the preform hasbeen disclosed (refer to JP-A-8-142175). Such a technique, however, hasthe following problem. That is, since both of those means have to bemade operative almost simultaneously, the heating time cannot besufficiently shortened. Further, since heating equipment is large insize and complicated, a large installing space and the expensive cost ofequipment are necessary.

The invention is, therefore, made to solve the problems in the priorarts as mentioned above and it is an object of the invention to realizea technical subject which enables heat sources to operate with a highpower upon heating of a preform and to thereby accomplish a largereduction of heating time of the preform and miniaturization of a wholepreform heating device.

DISCLOSURE OF INVENTION

As means of the invention according to Claim 1 among the inventions forsolving the above technical problems, there is provided a method ofheating a preform, whereby the preform which has been injection moldedinto a cylindrical shape with a bottom and is made of a PET is heated byheat sources in order to be biaxially stretched and blow molded into abottle shape, comprising the steps of:

to the preform, executing a first heating process to set the heatsources into a high power state while blowing out cooling air to thepreform and quickly heat the preform until a temperature of an outersurface of the preform is equal to a temperature value which is slightlylower than a crystallization temperature of the PET;

executing a temperature adjusting process to leave the preform until atemperature difference between the temperature of the outer surface anda temperature of an inner surface of the preform is equal to or lessthan a predetermined value in a state where the heating by the heatsources and the cooling by the cooling air are not executed;

executing a second heating process to heat the preform after completionof the temperature adjusting process by the heat sources until the outersurface temperature of the preform is equal to a temperature value whichis slightly lower than the crystallization temperature of the PET whileblowing out the cooling air to the preform;

sequentially executing the first heating process, the temperatureadjusting process, and the second heating process; and

setting the temperature difference at the end of the temperatureadjusting process to a value which is equal to or less than apredetermined value in which the inner surface temperature of thepreform at the end of the second heating process is equal to atemperature value in which an inappropriate stretching is not occurredon the inner surface side of the preform.

The crystallization temperature of the PET denotes a temperature atwhich crystallization occurs in a process in which the temperature ofthe preform is raised from a neighborhood of a room temperature.

In the first heating process, in a state where the cooling air is blownonto the outer surface of the preform, the preform is heated by the heatsources in a high power state. Therefore, in a state where the heatingof the outer surface is suppressed by the cooling air, the preform isquickly heated by the heat sources.

As mentioned above, since the heating of the preform by the heat sourcesis accomplished in the state where the heating of the outer surface ofthe preform is suppressed, as a whole preform, it is quickly heated bythe high power of the heat sources in a state where a temperature risingspeed of the outer surface is slightly suppressed. However, since theheat sources are in the high power state, the blow-out of the coolingair to the preform not only suppresses the temperature rising speed ofthe outer surface of the preform but also prevents the occurrence of aproblem such as carbonization or the like due to the overheat of theouter surface of the preform.

Therefore, since the quick heating of the preform is executed in a statewhere a difference between the temperature rising speed on the outersurface side and that on the inner surface side is set to be small, evenif the preform is quickly heated until the outer surface temperature ofthe preform is equal to a temperature value which is slightly lower thanthe crystallization temperature of the PET, the temperature differencebetween the outer surface temperature and the inner surface temperatureof the preform is not so large.

When the temperature adjusting process is performed to the preformsubjected to the first heating process, the outer surface side portionof the preform is cooled by the atmosphere, so that its temperature isreduced. On the other hand, the inner surface side portion of thepreform is heated by the heat that is transferred from the outer surfaceside portion and its temperature rises. The temperature differencebetween the outer surface temperature and the inner surface temperatureis set to be equal to or less than a predetermined value, that is, avalue in which the inner surface temperature of the preform at the endof the second heating process is equal to a temperature value in whichan inappropriate stretching is not occurred on the inner surface side ofthe preform.

When the second heating process is performed to the preform subjected tothe temperature adjusting process, to the outer surface, that is, whilethe temperature rising speed on the outer surface side is suppressed,the heating process is performed to the preform so that the heatingdistribution of the preform shows a predetermined pattern. Therefore,when the temperature difference between the outer surface temperatureand the inner surface temperature of the preform lies within a rangewhere no trouble is caused in the biaxial stretching blow moldingprocess to the bottle shape of the preform, the preform is heated untilthe outer surface temperature of the preform is equal to a temperaturevalue which is slightly lower than the crystallization temperature ofthe PET.

According to the invention of Claim 1 as mentioned above, since thepreform is heated while the outer surface portion of the preform whichis heated strongest is cooled by the first heating process, the quickheating can be sufficiently performed to the preform withoutoverheating. Thus, the heating time of the preform can be remarkablyreduced. After the difference between the outer surface temperature andthe inner surface temperature of the preform which is caused by thefirst heating process is corrected and restricted within thepredetermined range by the temperature adjusting process, the secondheating process is performed while blowing the cooling air in a mannersuch that the preform is set to the constant temperature distributingpattern and the temperature difference between the outer surface and theinner surface of the preform is not increased. Thus, the preform can beheated in accordance with the set temperature distribution in a statewhere the temperature difference between the outer surface and the innersurface of the preform which is biaxially stretched and blow molded intothe bottle shape is certainly positioned within the proper range.

The invention of Claim 2 is obtained by adding the followingconstruction to the construction of the invention of Claim 1: theheating by the heat sources to the preform in the second heating processis performed in a manner such that partition plates are arranged among aplurality of heat sources so that a temperature distribution along theaxial direction of the preform shows a desired pattern.

In the invention of Claim 2, since a heating portion of the preform byeach heat source can be almost accurately set and restricted, theheating distribution along the axial center of the preform due to thesecond heating process can be set to an almost desired distribution.Thus, the bottle shape which is molded can be set to a thicknessdistribution.

According to the means of the invention of Claim 3, there is provided adevice for heating a preform which has been injection molded into acylindrical shape with a bottom and is made of a PET by heat sources inorder to be biaxially stretched and blow molded into a bottle shape,wherein: the inside of an outer shell arranged so as to surround aconveying path of the preform is divided and formed by partitions into afirst zone for performing a first heating process, a third zone forperforming a second heating process, and a second zone, positionedbetween the first and third zones, for performing a temperatureadjusting process; and in each of the first and third zones, the heatsources along the conveying path are arranged on one side of theconveying path and a panel for blowout ports in which blowout portsthrough which cooling air is blown out are opened and formed along theconveying path is arranged so as to stand on the other side of theconveying path so as to face the heat sources.

According to the invention of Claim 3, since each zone is divided andformed by the partition in the outer shell, an almost constantatmosphere is maintained with being hardly exercised by an influencefrom the outside and an influence among the zones.

In the first zone, the preform which is revolving and move along theconveying path is subjected to the first heating process such that theheating process by the heat sources is executed from one side of theconveying path and, at the same time, the cooling process by the coolingair is executed from the other side as an opposite side of the conveyingpath, so that the heat sources are set to the high power state withoutsetting the outer surface portion of the preform into the overheatingstate, thereby accomplishing the quick heating of the preform.

In the second zone, since it is a portion having a substantial hollowspace structure without the heating processing mechanism by the heatsources and the cooling processing mechanism by the cooling air, thepreform moved from the first zone to the second zone enters a statewhere it is left in the second zone, and owing to the heat transferringoperation in the preform, the temperature difference between the outersurface temperature and the inner surface temperature is set to be equalto or less than the predetermined value as a set temperature value, thatis, a value in which the inner surface temperature of the preform at theend of the second heating process is equal to the temperature value inwhich the inappropriate stretching is not occurred on the inner surfaceside of the preform.

In the third zone, there is executed the second heating process suchthat the heating process of the constant temperature distribution by theheat sources is executed from one side of the conveying path and, at thesame time, the cooling process to suppress a temperature rising degreeon the outer surface side of the preform is executed by the cooling airfrom the other side as an opposite side of the conveying path. Thus, thepreform is heated in accordance with the set temperature distributionwithout increasing the temperature difference between the outer surfaceside and the inner surface side of the preform.

The invention of Claim 4 is obtained by adding the followingconstruction to the construction of the invention of Claim 3: arectifying plate member for guiding the blowout cooling air to theoblique upstream side of the conveying path is attached to an openingedge of the blowout port of the panel for blowout ports on thedownstream side along the conveying path of the preform.

In the invention of Claim 4, since the cooling air from each blowoutport is blown out to the oblique upstream side of the conveying path,the cooling air from each of the blowout ports formed at regularintervals in the panel for blowout ports is blown out to each preformmoving on the conveying path in a continuous state. The constant coolingoperation is continuously applied to the preform.

The invention of Claim 5 is obtained by adding the followingconstruction to the construction of the invention of Claim 3 or 4: thesurface of the panel for blowout ports on the conveying path side isused as a reflecting surface for reflecting the light from the heatsources.

In the invention of Claim 5, the light from the heat sources whichpenetrated the conveying path can be reflected by the panel for blowoutports and irradiated to the preform without being irradiated to thepreform, so that heating efficiency of the preform by the heat sourcesis improved.

The invention of Claim 6 is obtained by adding the followingconstruction to the construction of the invention of Claim 3, 4, or 5:near infrared heaters are used as heat sources.

In the invention of Claim 6, since the heating of the preform isaccomplished by absorption of the near infrared light which isirradiated from the near infrared heaters, the heating speed on theinner surface side of the preform can be raised. Thus, the heating speedof the preform can be further increased.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic constructional plan view showing an embodiment ofa device of the invention.

FIG. 2 is a schematic constructional vertical sectional view of a firstzone in the embodiment shown in FIG. 1.

FIG. 3 is a schematic constructional vertical sectional view of a secondzone in the embodiment shown in FIG. 1.

FIG. 4 is a schematic constructional vertical sectional view of a thirdzone in the embodiment shown in FIG. 1.

FIG. 5 is an arrangement relational diagram of heat sources and a panelfor blowout ports in the embodiment shown in FIG. 1.

FIG. 6 is a whole front view of the panel for blowout ports shown inFIG. 5.

FIG. 7 is a temperature characteristics diagram for use in explanationof the heating operation of the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the invention will be described hereinbelow withreference to the drawings.

FIGS. 1 to 6 show the embodiment of a device of the invention. Thedevice is formed by a turntable, a chain, and the like. A longrectangular cylindrical outer shell 6 made of a heat resisting materialis arranged along a conveying path R for conveying a preform P held to amandrel 8 in a headstanding posture while revolving the preform togetherwith the mandrel 8 so as to surround the conveying path R. The inside ofthe outer shell 6 is divided by partitions 7 made of a heat resistingmaterial in order of a first zone A, a second zone B, and a third zone Cfrom the upstream side of the conveying path R (refer to FIG. 1).

The first zone A (refer to FIGS. 1, 2, and 5) is constructed as follows.Near infrared heaters serving as a plurality of heat sources 1 extendingalong the conveying path R are arranged on one side of the conveyingpath R in parallel along the axial center direction of the preform P. Onthe other side of the conveying path R, a panel 3 for blowout ports inwhich a plurality of blowout ports 4 which are long in the longitudinaldirection are opened at regular intervals along the conveying path R andwhich is assembled to a front edge of a duct for guiding cooling air eis arranged so as to stand facing the heat sources 1 as near infraredheaters. A first heating process (a) is executed to the preform P.

The surface (surface which faces the heat sources 1) of the panel 3 forblowout ports (refer to FIGS. 5 and 6) is used as a reflecting surfacefor reflecting near infrared rays k. A rectifying plate member 5 forguiding the cooling air e which is blown out from the blowout ports 4 tothe oblique upstream side of the conveying path R is provided for oneside edge (side edge serving as a downstream side of the conveying pathR) of each blowout port 4 so as to be in a half blanking shape and in anobliquely standing posture.

The second zone B (refer to FIGS. 1 and 3) has a hollow space structurewithout heat processing means such as heating means, cooling means, etc.for the preform P. The second zone B is divided so as to be in a statewhere it is shut off as much as possible from both of the neighboringfirst zone A and third zone C with respect to the atmosphere,particularly, thermal atmosphere, and a temperature adjusting process bis executed.

In the third zone C (refer to FIGS. 1 and 4), in addition to theconstruction of the first zone A, partition plates 2 for restricting anirradiating range of the near infrared rays k which are irradiated fromeach heat source 1 onto the preform P are added among the heat sources1. A second heating process c as a final heating process is executed tothe preform P.

FIG. 7 shows an example of change characteristics of an outer surfacetemperature Ta and an inner surface temperature Tb of the preform (P)which is heated by the method of the invention. Each processing time isdetermined in accordance with values of the outer surface temperature Taand the inner surface temperature Tb at the time of each process in amanner such that the outer surface temperature Ta at the end of theheating process of the invention lies within a range from 100 to 120° C.and the inner surface temperature Tb lies within a range from 85 to 105°C.

The first heating process (a) in the first zone A is a quick heatingprocess in which the heat sources 1 are made operative by a power of100%. Although the first heating process (a) is finished at timing whenthe outer surface temperature Ta reaches a first temperature Ta1 withina range from 110 to 120° C. that is slightly lower than acrystallization temperature of the PET, first heating time t1 as time ofthe first heating process (a) is equal to 7.3 seconds. A firsttemperature Tb1 as an inner surface temperature Tb at the end of thefirst heating process (a) lies within a range from 70 to 80° C. Atemperature difference between the first temperature Ta1 and the firsttemperature Tb1 has a large value of 40° C.

The temperature adjusting process b in the second zone B is finished atthe following timing: the preform P which was quickly heated to adesired temperature by the first heating process (a) is left in theconstant atmosphere without performing the heating process from theoutside, so that the outer surface temperature Ta is decreased by heatirradiation, the inner surface temperature Tb is increased by heattransfer from the outer surface side portion of the preform P, and atemperature difference s between a second temperature Ta2 of the outersurface temperature Ta and a second temperature Tb2 of the inner surfacetemperature Tb is equal to a preset temperature 10° C. which is equal toor lower than a predetermined value (according to a result ofexperiments, 20° C. for the present). However, temperature adjustmenttime t2 as time of the temperature adjusting process b is equal to 4.0seconds. The second temperature Ta2 of the outer surface temperature Taat the end of the temperature adjusting process b lies within a rangefrom 90 to 100° C. The second temperature Tb2 of the inner surfacetemperature Tb lies within a range from 80 to 90° C.

According to the second heating process c in the third zone C, an outputdegree of each heat source 1 is individually set to a predeterminedvalue and the preform P is heated so as to obtain desired temperaturedistribution along its axial center. The second heating process c isfinished when a third temperature Ta3 of the outer surface temperatureTa reaches a temperature of 100 to 120° C. which is slightly lower thanthe crystallization temperature of the PET. However, second heating timet3 as time of the second heating process c is equal to 6.0 seconds. Athird temperature Tb3 as an inner surface temperature Tb at the end ofthe second heating process c lies within a range from 85 to 105° C. Atemperature difference between the third temperature Ta3 and a thirdtemperature Tb3 is equal to 15° C. at which there is no problem when thepreform P is biaxially stretched and blow molded into a bottle shape.

In the second heating process c in the third zone C, the reason why thetemperature difference between the outer surface temperature Ta and theinner surface temperature Tb is not so large in spite of the fact thatthe second heating process c is quick heating of a certain extent isbecause the outer surface of the preform P is forcedly cooled by thecooling air e.

According to a result of the actual measurement of the invention, timewhich is necessary for heating the preform P at an ordinary temperatureuntil a temperature at which it can be biaxially stretched and blowmolded into a bottle shape, that is, total time of the first heatingtime t1, the temperature adjustment time t2, and the second heating timet3 is equal to (7.2+4.0+6.0=17.2) seconds and equal to almost half ofthe conventional one. Thus, a length of heating device along theconveying path R can be set to half of the conventional one.

Each of the first heating time t1, the temperature adjustment time t2,and the second heating time t3 changes in dependence on a difference ofan average thickness of a body portion including a bottom portion of thepreform P in accordance with a tendency such that the thicker theaverage thickness is, the time becomes slightly long. However, the totaltime is similarly equal to about half of the conventional one.

EFFECTS OF THE INVENTION

Since the invention has the construction mentioned above, the followingeffects are obtained.

According to the invention of Claim 1, since the preform is heated whilethe outer surface portion of the preform is cooled, the outer surfaceportion which is heated strongest can be safely and quickly heatedwithout setting it into the overheating state. Thus, the remarkablereduction of the heating processing time of the preform is accomplishedand the remarkable improvement of the efficiency of the biaxialstretching blow molding operation is accomplished.

Since the large temperature difference between the outer surface sideand the inner surface side of the preform which is caused by the forcedheating from the outside is decreased by the temperature adjustingprocess to the value in which the good biaxial stretching blow moldingprocess can be certainly obtained, the proper and good biaxialstretching blow molding operation can be stably obtained.

Further, since the heating of the preform to the preset temperaturedistribution is accomplished by forcedly cooling the outer surfaceportion of the preform so that the temperature difference between theouter surface side and the inner surface side of the preform is not solarge, the heating of the preform to the preset temperature distributioncan be naturally, smoothly, and quickly accomplished.

In the invention of Claim 2, the heating distribution of the preform bythe second heating process can be set to the almost desireddistribution. Thus, the thickness distribution of the bottle shape whichis molded can be set. In the second heating process of the preform,since the heating process can be accomplished while suppressing theincrease in temperature difference between the outer surface side andthe inner surface side of the preform, the heating process of thepreform to the temperature suitable for the biaxial stretching blowmolding can be safely accomplished.

According to the invention of Claim 3, since the first zone and thethird zone can be easily constructed and the zones can be easily dividedand formed, the invention of Claim 1 can be easily and preferablyembodied.

Since the desired heating process to the preform can be completed in ashort time, a length of line which is required for the heating processcan be reduced. Thus, a length along the conveying path of the preformof the heating device can be decreased, so that sufficientminiaturization of the heating device can be accomplished.

According to the invention of Claim 4, since the cooling air can beblown out in a continuous state to each preform which is moving on theconveying path, the constant cooling operation can be continuouslyperformed to the preform. Thus, the stable and certain overheatpreventing operation to the preform can be obtained.

According to the invention of Claim 5, since the heating process of thepreform by the heat sources can be efficiently accomplished, the ratedvalues of the heat sources and the electric power which is required forheating can be reduced.

According to the invention of Claim 6, since the heating of the preformcan be accomplished in a state where a large temperature difference isnot caused between the outer surface side and the inner surface side ofthe preform, the more rapid heating process of the preform can beobtained and the heating time can be further decreased.

1. A method of heating a preform, whereby the preform (P) which has beeninjection molded into a cylindrical shape with a bottom and is made of apolyethylene terephthalate resin is heated by heat sources (1) in orderto be biaxially stretched and blow molded into a bottle shape,comprising the steps of sequentially executing the following processesto said preform (P): a first heating process (a) to set said heatsources (1) into a high power state while blowing out cooling air (e) tosaid preform (P) and quickly heat the preform (P) until a temperature(Ta) of an outer surface of said preform (P) is equal to a temperaturevalue which is slightly lower than a crystallization temperature of saidpolyethylene terephthalate resin; a temperature adjusting process (b) toleave the preform (P) until a temperature difference (s) between theouter surface temperature (Ta) and an inner surface temperature (Tb) ofsaid preform (P) is equal to or less than a predetermined value in astate where the heating by said heat sources (1) and the cooling by saidcooling air (e) are not executed; and a second heating process (c) toheat the preform (P) after completion of said temperature adjustingprocess (b) by said heat sources (1) until the outer surface temperature(Ta) of said preform (P) is equal to a temperature value which isslightly lower than the crystallization temperature of the polyethyleneterephthalate resin while blowing out the cooling air (e) to the preform(P), wherein said temperature difference (s) at the end of saidtemperature adjusting process (b) is set to a value which is equal to orless than a predetermined value in which the inner surface temperature(Tb) of said preform (P) at the end of said second heating process (c)is equal to a temperature value in which an inappropriate stretching isnot occurred on the inner surface side of said preform (P).
 2. A methodof heating the preform according to claim 1, wherein the heating by theheat sources (1) to the preform (P) in said second heating process (c)is performed in a manner such that partition plates (2) are arrangedamong a plurality of heat sources (1) so that a temperature distributionalong an axial direction of said preform (P) shows a desired pattern. 3.A device for heating a preform (P), which has been injection molded intoa cylindrical shape with a bottom and is made of a polyethyleneterephthalate resin, heat sources (1) in order to be biaxially stretchedand blow molded into a bottle shape, comprising: an inside of an outershell (6) arranged so as to surround a conveying path (R) of saidpreform (P) is divided and formed by partitions (7) into a first zone(A) for performing a first heating process (a), a third zone (C) forperforming a second heating process (c) wherein partition plates (2) arearranged among a plurality of heat sources (1) so that a temperaturedistribution along an axial direction of said preform (P) shows adesired pattern, and a second zone (B), positioned between said firstzone (A) and said third zone (C), for performing a temperature adjustingprocess (b); and in each of said first and third zones, the heat sources(1) are arranged along the conveying path (R) on one side of saidconveying path (R) and a panel (3) for blowout ports in which blowoutports (4) through which cooling air (e) is blown out are opened andformed along said conveying path (R) is arranged so as to stand on theother side of said conveying path (R) so as to face said heat sources(1).
 4. A device for heating the preform according to claim 3, wherein arectifying plate member (5) for guiding the blowout cooling air (e) toan oblique upstream side of said conveying path (R) is attached to anopening edge of said blowout port (4) of said panel (3) for blowoutports on a downstream side along said conveying path (R).
 5. A devicefor heating the preform according to claim 3, wherein a surface of saidpanel (3) for blowout ports on the side of said conveying path (R) isused as a reflecting surface for reflecting light from said heat sources(1).
 6. A device for heating the preform according to claim 3, whereinnear infrared heaters are used as said heat sources (1).
 7. A device forheating the preform according to claim 4, wherein a surface of saidpanel (3) for blowout ports on the side of said conveying path (R) isused as a reflecting surface for reflecting light from said heat sources(1).
 8. A device for heating the preform according to claim 4, whereinnear infrared heaters are used as said heat sources (1).
 9. A device forheating the preform according to claim 5, wherein near infrared heatersare used as said heat sources (1).
 10. The method of heating a preformaccording to claim 1, wherein in the first heating process (a) thepreform (P) is heated to a temperature (Ta) from 110° C. to 120° C. 11.The method of heating a preform according to claim 1, wherein in thefirst heating process (a) the preform (P) is heated in less than 10seconds.
 12. The method of heating a preform according to claim 1,wherein in the temperature adjusting process (b), the temperaturedifference (s) is less than 20°.
 13. The method of heating a preformaccording to claim 1, wherein in the second heating process (c) thetemperature (Ta) is from 100° C. to 120° C.
 14. The method of heating apreform according to claim 1, wherein in the second heating process (c)the inner surface temperature (Tb) is 85° C. or more.